A common method of treatment used in restoring blood flow through a diseased segment of a blood vessel is balloon angioplasty. The therapy generally involves the use of a balloon catheter. The balloon catheter is introduced into the cardiovascular system of a patient through the brachial or femoral artery and advanced through the vasculature until the balloon attached to the distal end of the catheter reaches the diseased vessel. The balloon is placed across the diseased vessel segment and is inflated. The balloon is then deflated to a small profile, so that the balloon catheter may be withdrawn from the patient's vasculature and the blood flow resumed through the dilated artery.
Angioplasty of an artery to correct flow obstruction in the vessel may stimulate excess tissue proliferation which then blocks (restenosis) the newly reopened vessel. The physician may need to perform a second angioplasty procedure or perform a more drastic procedure, such as a surgical bypass operation. To reduce the likelihood of restenosis and to strengthen the diseased vessel segment, an intravascular stent may be implanted within the segment of the diseased vessel. The stent is typically transported through the patient's vasculature while the stent has a small delivery diameter. The stent is then expanded to a larger diameter, often by the balloon portion of the catheter.
Stents are tubular structures, which are radially expandable to hold a narrowed blood vessel in an open configuration. Stents are most often used to support blood vessels. Stents can also be used to reinforce collapsed or narrowed tubular structures in the respiratory system, the reproductive system, biliary ducts or any other tubular body structure.
Since a catheter and a stent travel through the patient's vasculature, the stent has a small delivery diameter. The stent is positioned on a balloon catheter, such that the stent does not interfere with the vasculature during delivery, and the stent does not slip off the catheter before the stent reaches the desired location for deployment.
A stent is typically crimped onto a balloon portion of a catheter to reduce the diameter of the stent and to prevent the stent from sliding off the catheter when the catheter is advanced through a patient's vasculature. Non-uniform crimping can damage the stent and/or may result in a compressed stent/catheter profile that is larger than intended. If a stent is not securely crimped onto the catheter, the stent may slide off the catheter and into the patient's vasculature prematurely. It is important to ensure the proper compression of a stent onto a catheter in a uniform and reliable manner.
Many devices have been proposed for crimping stents onto catheters. Crimping of metallic stents is usually performed by a plier-type crimping device that cause diameter reduction. With metal stents, use of a plier-type crimping device does not inhibit simultaneous elongation of the metal stent because of the relatively high mechanical strength and the low friction coefficient of the metal stent.